Space discharge system



, ly 30, 1929' V J. c. SCHELLENG 1,722,987

SPACE DISCHARGE SYSTEM Filod' March 20 1924 //7 venfox? Jam 6 Joby/my Patented July 30, 1929.

UNITED STATES PATENT OFFICE.

JOHN C. SGHELLENG, OFEAST ORAllGE, NEWJEBSEY, ASSIGNOR'TOWESTERN ELEC- TRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

SPACE DISCHARGE SYSTEM.

Application filed March 20, 1924. Serial No. 700,554.

This invention relates to systems of space discharge devices and more particularly to a method of and means for providing an arrangement whereby separate units including three electrode devices of this type may be connected in parallel relation to each other with respect to external circuits.

An important object is to couple independent units, comprising space discharge devices, in parallel relation to each other with respect to an external circuit so that the production of spurious oscillations in the system is prevented.

A feature of this invention is the provision of reactive means included in a circuit common to separate space discharge units for connecting them in parallel to each other with respect to an external circuit so that inter-unit singing does not occur.

l/Vhen considerable numbers of space discharge devices are to be connected in parallel relation, it often becomes necessary, as a matter of constructional convenience or for other reasons, to locate one bank on a panel a little r removed from one or more other banks and to connect the several banks in iarallel relation. A phenomenon which may be described as interbank singing then often occurs. In the limiting case each bank may consist of a single device, but the utility of this invention and its applicability in practice relate principally to the case where each bank of tubes consists of a considerable number i. e. ten in a specific case.

A general object of the invention is, therefore, to reduce interbank singing or the production of free oscillations. These oscillations are especially undesirable in cases where the system is to be used for faithfully reproducing waves of a selected frequency or frequency baud impressed on the input circuit of the system, as in carrier wave signaling. Thefree oscillations may cause interruptions to service by producing serious overloads or abnormally high potentials and the latter may endanger the apparatus.

A nrong other disadvantages, the production of free oscillations often prevents the system from operating at the desired frequency, causes distortion of the wave form to be repeatcd, wastes energy by diverting it from a useful purpose, thereby reducing the chiciency of the system, and may cause serious ever heating of the circuit conductors and lead-in wires of the electrodes of the discharge devices, whereby the devices are liable to be destroyed.

The production of free oscillations in a system of the type described above is in general due to the cyclic transfer of energy from the anode circuit of the system to the grid circuit, the amplitude and phase of the resulting grid potentials, relatively to the corresponding anode potentials, being such as to set up and maintain a current flow in the system. The frequency of the free oscillations is determined by the inherent reactances of the sys tem. The inherent reactances of a system of this kind may be defined as the grid-filament, grid-plate and filament-plate capacities of the discharge devices. the capacities of these elements to earth and to other ap iaratus, together with the inductances and capacities of the conductors interconnecting the devices, and those connecting them with the associated input and output apparatus.

The present invention provides a reactive device, adapted to be included in the circuit connecting the separate space discharge units, for eliminating the tendency to produce undesired oscillations in the system.

In accordance with this invention a reactive device, comprising an inductance having a resistance connected in parallel thereto, has its terminals connected to the common conductors or bus-bars for the corresponding electrodes of the discharge devices of the different units and has an intermediate point of the elements of the reactive device connected together and to the common circuit connecting the input or output apparatus to the space discharge system.

The novel features and combinations which are believed to be ciaractcristic ofthe invention will be set forth with particularity in the appended claims. The invention itself, however, as to both its organization and meth 0d of operation will best be understood by reference to the following description taken in conjunction with the attached drawings in which,

Fig. 1 illustrates a radio transmitting sys tern including the invention as applied to the grid circuit of two banks of tubes, and

Fi 2 illustrates a similar system in which the reactive device constituting the invention. is a )pllQCl to the plate or anode circuit of a two bank set.

Referring now .rto Fig. 1 there are shown two .units 1 and 2 .each con'iprising .a plurality of parallel connected space discl' ange amplifiers. 3.

The impedance control electrodes of the tubes 3 of each group are connected to a common bus-bar 4. The bus-bars areconnectcd together by a circuit including the device 5 which comprises parallel connected inductance 6 and resistance 7.

Asource S-supplies high frequency waves throughthetransformerf) and lead 10 to "the intermediate point of the parallel connected I'CtlCtlVQllGVlCO 5.

V ThecoilG should be so wound that the-two sections are inductively coupled and their inductances are additive,ras viewed from bank to hanlk. The co-eilicicnt of mutual =inductance for the-two portionsof coil fishonld be high as possible, since the higher the inn- -tualinductance the lower-"the impedance of coil 6 for the waves to'be amplified.

.A-resistance ll is'ccnnected in shunt-to the secondary winding of-t he transformer 9, one terminal of which is connected toground at 12. The resistance 11 is of such magnitude relatively to the internal impedance of the discharge devices, thattheyoperate to repeat faithfully the high frequency waves without distortion.

The source 13 supplics,throug'h a-filterle, a

olarizin aotential to the im edance con- ,densers.

trol electrodes ofthe'amplifiers 8. The filter 14c functionsto suppress voltage variations of the source 13,-whereby aconstant potential is impressed u impedance, about the-transformer secondary,

for-thehigh frequency waves supplied by the source'8.

The input circuit of the amplifiers extends from ground 12 throughthe parallel connected secondary winding of the transformer 9 and resistance 11, conductor 1.0,ii1terniediate point of the device 5 to the bus-bars 4:, control electrodes of the devices 3 of groups 1 and 2, their cathodes, condensers shunting the secondaries oftransformer 16, leads 18 to ground 51-7 and thence back to ground at 12.

Space current is supplied by the source 19 to the two groups of amplifiers connected in parallel with respect thereto, through the may betraced as follows.

blocking condenser 23 prevents direct current, from flowing through the transformer 24;. V

The space current path of the amplifiers From the positive terminal of the source 19, choke coil 20, plates of thedischarged devices included in groups 1 and 2, their cathodes, the secondaries of the transformers 16, leads 18: 0 ground-at 17 and back.through-ground to the negativeterminal of the source 19.

Amplified high frequency waves produced in the outputcircuits of :the amplifiers are supplied {through :the blocking condenser 23 to the tuned-circuit comprising the primary -.Winding ofthetransformer Qtandcondenser 25 connected in parallel thereto.

Thechoke coil 20 servestoprevent theflow of high frequency wavesto ground through the source .19 and the transformer 241 supplies the amplified waves to the antenna 26.

Where theseparate units are connected to input and output apparatusesbycommon connections, undesired oscillatory waves, flowing through the circuit formed thereby, may be fed back tO thecont-rol element through any coupling interconnecting them, as for example, through the interelectrode capacities within. the devices. Conditions may be i such that .sustainetl oscillations will he produced in the circuits of the system.

Illeferringto the statement above describing the :inputcircuit-ofthe amplifier system, it willlhe seen that the high frequency .volt age Waves produced in secondary of transformer 39 by the source 8 are transmitted through theconductor 10-tothe intermediate pointof the inductance 6 and .areefi ective through parallel paths. Each path extends from one terminal o'fthe secondary winding of thetransformeril, through one portionof the coil 6 in parallel with one .portion of resistance 7, the space path between the control electrodes and cathodesof the amplifiers of groups 1 or 2, condensers shunting :the secondary winding of transformers 116, ground 17 of group 101' 2'to ground at '12and thence tothe otherterniinal ofthe secondary winding of 9.

Undesiredoscillatoryimpulses may be fed backthrough the ingterelectrode capacities of the amplifiers and hence-tend to flow from one bus bar l to theothcr bus bar 1- through the reactive device-5.

By designing .the coils 6 so that the impedance thus inserted in lead 10 for-currents of the frequency to be amplified is small,

while that of the whole-coil is high for the undesired oscillatory impulses, and using a shunting resistance adapted to impose a high damping effect for high frequency currents, the undesired impulses will in part be prevented from traversing the coil 6 and hence will in part be diverted to the shunt path including the resistance 7, by which they .Will be suppressed or dissipated.

In Fig. 2 there is shown a radio transmitting system, which is similar to that illustrated in Fig. 1, in which like parts are identified by like reference characters.

The circuit of Fig. 2 differs from that shown in Fig. 1 as follows, a polarizing potential is impressed upon the control electrodes of the amplifiers 8 of the two units by a battery 27 directly connected between the resistance 11 and ground 12, and the reactive device 5 is included in the common output connection for the amplifier units 1 and 2.

In this case the amplified energy is supplied from the units 1 and 2 through the two portions of the coil 6 in parallel, while spurious oscillations are impressed upon a path connected to the terminals of the reactor 5. The design of the reactor 5 is similar to that dcscribed above. The two sections of the inductance 6 and its shunting resistance 7 are in series for currents circulating between the two units and hence these impulses will be diverted in part by the coil 6 to the resistance 7, by which they Will be suppressed or dissipated.

lVhile in the preceding description the amplifier units or banks 1 and 2 are shown as consisting of three parallel connected discharge devices 3, it is to be understood that the principles of this invention may be applied toa system having any number of discharge devices, one or more in each unit, and may be used with banks or units each having a different number of discharge devices, whether adapted tooperate at high or low power.

Where an equal number of discharge devicesare included in each bank or unitthe input or output apparatus should be connected to the midpoint of the reactive device.

lVhen the number of discharge devices included in the units is unequal, the input or output apparatus should be connected to the reactive device so. that the impedance of the sections of the reactive device, for waves of the frequency to be repeated, between the point of connection and the respective units is inversely proportional to the number of discharge devices in the units.

Thus, if the first unit includes N discharge devices and the other units l discharge devices, the connecting point for the input or output apparatus, should be such that M Ll2- L +M R N where L represents the self-inductance of the inductance coil section between the first unit and the connecting point and similarly L represents the self-inductance ofthe coil section between the connecting point and the second unit.

If desired the input and'output arrangements of the invention, as disclosed with reierence to Fig. 1 and 2 respectively, may be jointly used in a single circuit.

This method of preventing interunit ing has been applied with good cii'ect to radio telephone system cmployin two banks. including ten discharge devices each adapter! to respectively deliver approximately 10 kilowatts at about (50,000 cycles through its output circuit. Space current was supplied to the anodes of the discharge devices at about 10,000 volts.

In the arrangement just described the individual tubesof each bank were provided with additional means, not herein (lESClll'JQCl, adapted to prevent singing because of the coupling etfectsbetween the input and output circuits of discharge devices included therein. Each bank as a whole may also be provided with any suitable m ans to prevent intertube singing between the tubes of the bank without interfering with the functioning of the elements of the present invention.

The reactive device in this case consisted of a coil approximately 3 inches in diameter, inches long, having 22 turns per inch and its inductance was .125 millihenry and a resistance of 600 ohms connected in parallel to the coil.

This invention maybe used with any even number of pairs of banks, i. e. 4:, 8, 10, etc, by connecting each pair as hereinbefore described through a reactive device, the pairs in a similar manner through additional reactive devices and finally the interconnecting conductor for the groups of banks through a reactive device to a single conductor "for connecting them to either the input or output apparatus.

Again it is to be understood that this invention is not to be limited to specific de tails described above, but only by the scope of the attached claims.

,lVhat is claimed is:

1. In a space discharge system comprising a plurality of parallel connected units each unit conunis'ing a bank of space discharge devices, the method of preventing interbank singing in the system which comprises impressing undersired oscillations upon a path of high impedance connecting said banks, and transmit-ting oscillations of desired frequencies through a part of said path which is of low impedance therefor.

2. A space discharge system comprising a plurality of unitseach including three-elec strode s ace dischar e devices an external circuit, and means for connectingsaid units in parallel with respectto said circuit comprising a reactance element having its terminals conncctedto said units and an intermediate point thereotconnected to said circuit.

3. A space discharge system comprisinga plurality of units each including three-electrode space discharge devices, an external circuit, and means tor-connecting said units in parallel With respect to said circuit comprising a reaetance element having its terminals connected to said units and at least a portion of said element connected between each unit and saidcircuit.

4. A space discharge system including a plurality of unitseach including at leastonc three-electrode space discharge device, an

external circuit, and means for connecting said units in parallel with respect to said circuit comprising a reactaiice element having its terminals connected tocorresponding .electrodesof the device-included in said units and an intermediate pointccnnected to said circuit. 1

5. A space discharge-system comprising a plurality of unitseach including at least one three-electrode space discharge device.

means for causing said units to operate simultaneously,comprising a reactor, the corresponding electrode of the device included in each unit being connected by a conductor to a terminal of said reactor, a portion of said reactor being connected between each unit and aeircuit external to said units.

6. A spacedischarge system comprisinga plurality of units parallel connected, relative- 1y to an external circuit, by means comprising a path of high llllPQClllIlCGjfOl' undesired oscillations in series between said units and a path of low impedance ,for desiredoscillations bctweeneach of said units andsaid circuit. 7

7. Ina space discharge system includinga plurality of parallel connected space dis charge units, the method of-preventing the production of undesired oscillations in the system which comprises causing oscillations of desired irequencies from the respective units to traverse parallel conducting paths therefor, and impressing oscillations .Of iindesired frequencies upon a path, including in series portions oi said parallelpaths, to-control the suppression oi said undesired oscil- ,lations.

In a space discharge system including a plurality of parallel connected space discharge units, the method of preventing the production of undesired oscillations in the system which comprises causing oscill'ationsof desired frequencies from the respective units to traverse parallel conductive paths there'- for, and impressing oscillations of undesired frequencies upon a path includingin series portions of said parallel paths whereby said electrodes thereoi';

undesired O cillations aredi-verted to a conductive suppression pathasscciated with the said series portions. i

A .space discharge system-comprising a plurality of unitscach including three-elem trode space discharge devices, means for causingsaidnnits ,to operate simultaneously, and a reactance eleiiieiit'having'its terminals connected to the correspondingelectrodes of said unitsand its midpoint connected to a circuit external to said units.

10. A space discharge system comprising a plurality of units'each including three-electrode space discharge devices, a reactance device comprising an inductance and resistance connected in parallel having its termi nals connected to the corresponding electrodes of said units and its midpoint connected to an external circuit.

11; A space discharge system comprising a plurality of ,units each including three-electrode space discharge devices having their corresponding electrodes connected to a commonconductor, an external circuit, and means'itor connecting said units in parallel withrespectto said circuit comprising a reactor having its terminals connected to said common conductors and its midpoint connected to said circuit.

ance, and acircuit extending from an intermediate point on said inductance and resistance to the cathodes oi said tubes.

1 In a space discharge system, a first group of dischargedevices connected in parallel, aconnection between corresponding a second group of discharge devices connected in parallel, aconnection between corresponding electrodes thereof;' a conductive path extending b tween said first and said second connections incl'udinga reaetivedevice, an external circnit connected at a point on said reactive device such that the impedance of the reactive device between said external circuit connecting point and the connectors for the respective groups is inversely proportional to the number of discharge devices in the respective groups,

15. In a. space discharge system a unit comprising N discharge devices having corresponding electrodes connected in parallel, a second unit comprising N discharge devices having corresponding electrodes connected in parallel, an apparatus external to said units, a conductive path connecting the first unit to said apparatus including an inductance L and a resistance R, in parallel, a conductive path connecting the second unit to said 16. In a system comprising two physically separate banks, each bank comprising a plurality of parallel connected space discharge devices, means for causing simultaneous op eration of said units, and means for preventing singing comprising an interbank reactor including an inductance, connecting the entire group of parallel connected electrodes of one unit With the corresponding group of parallel connected electrodes of the other unit.

17. In a combination in accordance with claim 16, a resistance in shunt to the said in ductance and constituting an element of said reactor and a lead extending from an intermediate point of said reactor to external apparatus.

In Witness whereof, I hereunto subscribe my name this 19th day of March, A. D., 1924:.

JOHN C. SOI-IELLENG. 

